The present invention relates to a method for forming conductive bumps on pad patterns on a circuit board when a device such as an LSI is packaged to the circuit board of an electronic unit of an electronic computer.
A method for forming conductive bumps of this type is disclosed in JP-A-1-73625 (Japanese Patent Application Serial No. 62-630406). As shown in a sectional view of FIG. 4, conductive metal balls 3 made of solder are sucked into recesses 2 formed thicknesswise of an alignment jig 1 to align thereto, and they are positioned such that the recesses 2 face to respective pad patterns 5 on a circuit board (or LSI) 4. Then, the conductive metal balls 3 are heated and fused to join and transfer the conductive metal balls 3 to the pad patterns 5, and the alignment jig 1 is removed to complete the circuit board (or LSI) 4.
DENSHI ZAIRYO, November 1992, p29, FIG. 1 and NIKKEI Electronics, Feb. 17, 1992, p105, FIG. 2 show similar methods.
Namely, as shown in FIG. 5, a film-like connector 7 having conductive metals (e.g. gold) 6 embedded at a predetermined interval are arranged between circuit boards 8 and 9, and the connector 7 is pressed by the circuit boards 8 and 9 to connect mating pad patterns 10 and 11 of the circuit boards 8 and 9.
flowever, in the method of forming the bumps shown in FIG. 4, the special alignment jig 1 is used to suck the conductive metal balls 3. Thus, it requires an air source and the work is troublesome and not efficient.
Further, in the method for forming the junction shown in FIG. 5, the circuit boards 8 and 9 are used while the film-like connector 7 is left. Thus, the connector 7 may interfere the arrangement of other parts.